Nano particles are particles having a nano-scaled particle size, and exhibit optical, electric, and magnetic characteristics completely different from those of a bulk-state material due to a quantum confinement effect in which the energy required for electron transfer is changed depending on the size of material, and a large specific surface area. Thus, due to these properties, much interests have been focused on the applicability in the fields of catalysts, electro-magnetics, optics, medicine, and the like. Nano particles may be an intermediate between bulk and molecule, and in terms of an approach in two ways, that is, a “Top-down” approach and a “Bottom-up” approach, it is possible to synthesize nano particles.
Examples of a method for synthesizing metal nano particles include a method for reducing metal ions with a reducing agent in a solution, a method using gamma rays, an electrochemical method, and the like. However, methods in the related art are problematic in that it is difficult to synthesize nano particles having a uniform size and shape, or the use of an organic solvent leads to environmental pollution, high costs, and the like. For these various reasons, it was difficult to economically mass-produce high-quality nano particles.
Meanwhile, in order to fabricate hollow metal nano particles in the related art, hollow metal nano particles have been fabricated by synthesizing particles with a low reduction potential, such as Ag, Cu, Co, and Ni, substituting the surface of particles, such as Ag, Cu, Co, Ni, or the like with a metal having a higher reduction potential than the particles with a low reduction potential, for example, Pt, Pd, or Au by a potential difference substitution method, and after the surface substitution, melting Ag, Cu, Co, Ni, and the like remaining inside the particles through an acid treatment. In this case, there is a problem in the process in that a post-treatment needs to be performed with an acid. Since the potential difference substitution method is a natural reaction, there are few factors that may be controlled, and thus it is difficult to fabricate uniform particles. Therefore, there is a need for a method for fabricating uniform hollow metal nano particles, which is easier than the methods in the related art.